Writing in the Sciences (in general) and Astronomy (in particular)
Tom Statler, Dept. of Physics & Astronomy, Ohio University
1. Good Writing vs. Bad Writing
Good writing is clear, compelling, logically organized, precise, and
interesting. Bad writing is opaque, unconvincing, disorderly, vague, and
boring. Whether you are writing science or fiction (or science fiction),
the same rules of good writing apply:
- Know your message. What are the most important things that you
want your reader to come away with?
- Know your audience. What base of knowledge do you share?
What do they already know, and what is it your job to explain?
- Present a connected argument. Does each sentence build logically
on the previous one? Does each paragraph deal with a single central
- Be precise. Have you said exactly what you meant to say, or just
something roughly in the ballpark?
- Be interesting. Are you using language in a reader-friendly way?
Good scholarly writing is difficult. Moreover, it can get more difficult
the better you know your subject. The reason is that an expert's understanding
of a subject is a multidimensional network of connections among many different
concrete facts and abstract concepts. Writing, on the other hand, is linear.
As an expert writer, it's your responsibility to create a comprehensible
one-dimensional path through that network, and to lead the reader through it
in a way that he or she can then begin to build his/her own network of
The worst writing of all is unoriginal writing, and specifically
plagiarized writing. Your writing must be your own creation. There
is no way to sugar-coat this: There are no circumstances under
which copying text from another source is acceptible. It doesn't matter
if you found a writer who says things more clearly and eloquently than you'll
ever be able to. Copying is wrong. Copying and making minor changes so that
it doesn't obviously look like an exact copy is even more wrong. So don't do it.
The point of this article is not to show you what the format of a scientific
paper looks like. I'm assuming that you have seen and read enough papers that
you are beyond that. Rather, my point is to alert you to specific writing
issues that are going to come up as you write the various sections of your
2. The Introduction
The function of the introduction is exactly what it says: you are introducing
your readers to a subject that they're not familiar with. You're also trying
to convince them that the particular topic you are addressing---which is
probably one tiny piece of a much bigger puzzle---is interesting and worth
reading about. You can lose your reader on page one with a poor introduction,
so keep this advice in mind:
- Start with the big picture. Step by step, narrow the focus to
arrive at your specific subject.
- At each step, give the reader specific information about what is
currently known and understood, citing relevant papers (thereby giving
credit to those who have contributed to this understanding).
- Also at each step, give the reader specific information about what
is not understood. If there is disagreement between different
researchers, explain the nature of the disagreement (with citations). Often,
this provides a natural transition to the next deeper level.
- Critique the logical flow of your presentation. Does each
sentence logically follow from or build on the previous one? Have you given
the reader all the information he/she needs to understand it? Make sure you
define terms before using them, and spell out acronyms the first time they
- The last paragraph (sometimes two) of the introduction is where you
finally arrive at your work. Be explicit about how your contribution adds to
the work that has come before. Don't discuss your conclusions; that comes
later. But if you've done your job, your reader will now be thinking that
it's obvious that somebody needs to do exactly what you have done.
3. The Main Body of the Paper
This is usually the easiest part of the paper to write. Here you are
reporting on what you did and what the results are, so the logical ordering
is often fairly intuitive. If you're writing an observational paper, you
will probably have a section on the observations, one on the data reduction
and analysis, and one describing the results. If you're writing a
theoretical or modeling paper, you'll have a description of the model
or the assumptions of the theory, followed by a derivation of the key
equations or a description of your numerical code, and then a presentation
of the results. I'm trusting you to know at a basic level what information
is essential for each of these sections.
But before you start writing, work through the following key issues:
Once you're clear on the above, make your figures. An advantage of this
strategy is that you can then write your text around the figures. But
remember that any figure or diagram must include:
- What is your most important result? What is the one thing
that you want the reader to remember from your paper?
- How can you best present that result? The answer is probably
"graphically"---which makes the issue how to design the one perfect
figure to show this one most-important thing.
- What other supporting figures would help the reader?
Remember, the goal is not for you to show everything you did, but for the
reader to understand the results.
A figure caption is not a substitute for a clear presentation and description
of the figure in the main text. Give the reader a guided tour of the figure.
Explain what is being plotted. Point out what the reader should notice, and
explain why it is interesting.
- Labeled axes, with numerical values and units;
- Error bars on any plotted data; and
- A caption, clearly explaining what is being plotted.
Precise language is especially important here. Be careful to say exactly
what you mean. If you mean "filter", don't write
"color"; if you mean "luminosity", don't write "magnitude".
the right word, not its second cousin. You need to communicate in
a way that will be understandable to somebody who has not been working
with you, and has not been sitting in
on your meetings with your advisor/professor.
Be conscious of the distinction between your private jargon and the proper
vocabulary of your discipline, and remember that it's your job, not the
reader's, to translate.
And although this is not strictly a point about writing,
one can't overemphasize the importance of the error analysis. Don't
shirk the responsibility to do a statistically legitimate error estimate on
any measured quantity. Guessing ("Oh, that's maybe good to 20 percent or
so...") doesn't count. If it doesn't have an error bar, it isn't science.
4. Discussion and Interpretation
This is, arguably, the most important part of the paper, and, sadly,
the one most often neglected by fledgling writers. You've explained your
methods and presented your results... but what does it all mean? It's
the author's job to put the results in context.
First comes the meaning of your quantitative results themselves. You may have
measured the central B-V color of M33 with unprecedented accuracy, but
so what? Your measurement has meaning only to the extent that it tells us
something about the natural world. This places a non-trivial
burden on you to understand (in this example) what physical
processes influence the optical color of a galaxy, and then to logically
infer what your measurement implies about those processes. Can you rule
out the presence of dust? Can you put a limit on the rate of star formation?
This exercise in logic will probably allow (i.e., require) you to revisit
the papers you cited in your introduction, and explain how your results
fit in with previously published work. Be forthright about where your work
agrees with or differs from others'. If there is agreement, be explicit about
what that implies; it may be increased confidence in some published model,
or a recognition that this particular object is unusual in an important way.
If there is disagreement, try to suggest a reasonable explanation, but
avoid unsupported speculation.
5. The End
It's traditional to end the paper with a recapitulation of the main results.
This conclusion can be very similar to the abstract, which has a similar
purpose. But the end of the paper is also an opportunity to
make a graceful exit from the maze of knowledge through which you have just
led your reader. Step back out to the big picture, and (without getting overly
theatrical) remind the reader how this new knowledge has bearing on our
overall understanding of this particular part of the universe, and, if
appropriate, how it sets the stage for future work.
6. Miscellaneous Sticky Points
- Active vs. Passive Voice. In some fields, active voice (e.g.,
"we observed the nebula", as opposed to "the nebula was observed") is
strongly frowned upon. In astronomy, active voice is encouraged. But, of
course, this doesn't rule out the use of passive voice where it is appropriate.
- Tenses. Generally, you should stick to present tense, even when you
are reporting on the past work of others; e.g., "Smith and Jones (1994)
show that dark matter dominates NGC8153." An exception is if you are talking
about work in a historical context: "This phenomenon was first discovered by
Zwicky (1930)." When describing your own observations and data reduction, you
can use past tense ("the data were flat-fielded using IRAF"); but the results
of that work should be described in present tense ("the flat-fielded image
contains 14 resolved sources"). Remember that statements about astronomical
objects should always be in present tense ("the galaxy has a strong color
gradient") unless you are specifically talking about a past event or an object
that no longer exists ("the supernova progenitor star was a type O supergiant").
- 1st vs. 3rd Person. In astronomy, writing in the 1st person is
encouraged (e.g., "we observed M51", "we show the results in Table 2",
etc.). In the case where there is only one author, opinions differ on whether
one should use the "editorial we", or merely charge ahead in 1st person
singular ("I"). The latter is more honest, and is becoming more common,
but it can sound annoying if it is overused.
6. Additional Resources
A Scientific Writing Booklet, from the Dept. of
Biochemistry & Molocular Biophysics
at the Univ. of Arizona. (Lots of advice on usage and grammar.)
The Science of
Scientific Writing, reprinted from American Scientist.
Excerpts from Michael Alley's The Craft of Scientific Writing,
along with exercises.
How to Write
a Scientific Paper, from the Annals of Improbable Research.
(Consider the source...)
Last updated 2008 May 30. Written and maintained by Tom Statler